Abstract This equipment request is for a compact IR spectrometer that will fit into an inert atmosphere glovebox which will enable the rapid and reliable characterization of transient intermediates at cryogenic temperatures. Our parent award involves the characterization of what secondary sphere effects influence the activity of metalloenzyme active sites. We are particularly interested in understanding how electric fields, coupled proton and electron transfer scaffolds, as well as specifically basic oxidizing intermediates enable activity and selectivity in oxidative transformations that underpin many biological pathways. Virtually all of the metal species involved in these pathways feature vibrationally active modes which both serve as vital characterization signatures as well as avenues for insight on the geometric or electronic structures of the proposed intermediates. Cryogenic Raman spectroscopy is an invaluable tool, but can be operationally challenging and also typically relies on resonance enhancement. We have looked at Raman spectroscopy extensively, but our complexes do not exhibit any resonance enhancement, rendering this technique difficult. This equipment request would provide us with a compact IR spectrometer that we can use in a glovebox. This is important as having this spectrometer in an inert atmosphere will both provide us with a way to work with reactive species, but will also enable us to do cryogenic experiments without any complications from moisture condensation. This is a significant advantage in characterization. We will use a cryogenically cooled heatsink, which can be prepared in a glovebox cold well, the provide cooling on an ATR platform on a commercial compact IR spectrometer from Bruker. This will enable us to add reagents in-situ and obtain reliable data on even highly reactive and transient intermediates. The new capabilities provided by this instrument will facilitate the characterization of several transient intermediates we are currently working with, and thus will greatly accelerate the rate of progress for this project.